More than 220 people from the London Fire Brigade, Metropolitan Police Service, London Ambulance Service and Urban Search and Rescue teams will be among those involved in the three-day exercise which is one of the largest and most comprehensive training exercises in history.

Millennium Mills, a derelict Victorian mill building, will be the scene of the devastation from midday on Saturday to midday on Monday.

The exercise will test local and national emergency response procedures in the event of a major incident in the capital.

Further details are being kept strictly under wraps until the exercise is underway on Saturday in order to make sure that the site remains a realistic training environment for the emergency service personnel taking part.

Docklands residents are being assured that they should not be concerned by the large number of emergency service personnel and vehicles that will be present in the area for the duration of the exercise.

Wayne Brown, London Fire Brigade’s Borough Commander for Newham, said: “These training exercises are vital to ensure that the emergency services are ready and prepared, should a major incident happen in the capital.”

He also reminded people to only dial 999 if there is a genuine emergency.